Midorikawa

It originates near Mt. Mukozaka on the border between Kumamoto and Miyazaki prefectures, flows west through central Kumamoto prefecture, and empties into Shimabara Bay at the base of the Uto Peninsula. It is the second largest river in the prefecture, with a length of about 76 km and a drainage area of ​​about 1,100 square km. Because it flows west along the Midorikawa fault line, it is said that before the construction of the Midorikawa Dam (1971), there were rapids, waterfalls, and gorges up to Idogoekyo in the middle reaches of the river. Even now, Yabe Shijuhachitaki waterfalls, Naidaijinkyo Gorge, and Ryokusenkyo Gorge attract many tourists as scenic spots, but the scenery has changed significantly since the construction of the Midorikawa Dam. At the point where the river flows out from the mountains onto the plateau in Kamitoyochi, Kosa Town, there is the remains of the first mechanized silk mill in western Japan. In addition, clever irrigation facilities have been devised to distribute water to the plateau at the foot of the mountains, which is poor in water, and new rice fields have been developed. The Midorikawa Dam not only regulates the water volume in the downstream area, but also supplies agricultural water to the Uto Peninsula and the northern part of the Yatsushiro Plain.

[Yamaguchi Morito]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

熊本・宮崎県境の向坂山(むこうざかやま)付近に源を発し、熊本県中部を西流し、宇土半島(うとはんとう)基部で島原湾に注ぐ一級河川。延長約76キロメートル、流域面積約1100平方キロメートルの県下第二の川。緑川断層線に沿って西流しているため、緑川ダム建設（1971）以前は中流域の井戸江峡までは急流、滝、峡谷が連なっていたといわれ、いまも矢部四十八滝、内大臣(ないだいじん)峡、緑仙峡などは景勝地として多くの観光客を集めてはいるが、緑川ダム建設後は著しくその景観を変えてしまっている。山地から台地に流れ出る地点の甲佐町上豊内(かみとようち)に西日本最初の工場制機械製糸工場跡がある。また、水に恵まれない山裾(やますそ)の台地にも巧みな水利施設の考案によって配水され、新田の開発がなされてきた。緑川ダム湖は、下流域の水量調整だけでなく、宇土半島、八代(やつしろ)平野北部にも農業用水の供給を行っている。

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